Systems that use modulating retro-reflectors for communications are well-known. One existing system employs modulating retro-reflectors to communicate optically and provides secure, high-speed data communications. However, existing communications systems that employ modulating retro-reflectors do not provide a flexible access control method for controlling communications among a probe device and a group of retro-reflectors, such that each of the retro-reflectors may receive schedule information regarding when respective retro-reflectors may be interrogated for data or may receive data. Further, a need exists for a system that permits a schedule for exchanging data between the probe device and any one of the retro-reflectors to be adjusted based on conditions, such as an amount of data to send or urgency of data.